Percutaneous access to the peritoneal cavity is necessary for uremic patients who must undergo peritoneal dialysis for treatment of acute or chronic renal failure. Such an access permits infusion of dialysis solution into the peritoneal cavity and drainage of dialysate-containing wastes that are convected or diffuse from uremic blood.
Typically a peritoneal catheter is implanted through the abdominal wall. Catheter implantation creates three segments: the intraperitoneal catheter segment is the part of the catheter located intraperitoneally; the intramural catheter segment is the part of the catheter contained within the abdominal wall; and the external catheter segment is the part of the catheter outside the skin exit.
The peritoneal catheter typically comprises a catheter body or tubing plus the cuffs. The tubing is typically made of soft material such as silicone rubber or polyurethane. A cuff is a band of fabric, affixed to the intramural segment of the catheter body, for fibrous tissue ingrowth to stabilize the catheter and to prevent pericatheter bacterial penetration.
A peritoneal catheter tunnel is surgically created during the implantation. The tunnel is a passageway through the abdominal wall within which the intramural segment of the peritoneal catheter is contained. The tunnel has an internal and external exit. The internal tunnel exit, or intraperitoneal tunnel entrance, is the inlet of the tunnel into the peritoneal cavity. The skin exit is the external exit or skin outlet of the tunnel.
The cuff located close to the endoabdominal fascia is called the epiperitoneal cuff, inner cuff, internal cuff, or deep cuff. The cuff located closer to the skin is called the subcutaneous cuff, outer cuff, superficial cuff, or external cuff. A part of the tunnel between the skin exit and the outer cuff is called the sinus tract. The exit site is the most external part of the sinus tract and the skin surrounding the skin exit.
Four major complications of the implantation and use of peritoneal dialysis catheters include external cuff extrusion, obstruction (which is usually, a sequel of catheter tip migration out of the true pelvis with subsequent omental wrapping), skin exit or tunnel (exit/tunnel) infection, and dialysate leaks. Peritonitis, particularly a refractory one, may also be related to peritoneal catheter design and care. These complications result in technical difficulties, morbidity, prolonged antibiotic therapy, catheter failure, and sometimes the inability to continue peritoneal dialysis. According to The National CAPD Registry Special Survey, in 1987, overall survival of the most commonly used catheters ranged between 10-30 percent at 3 years.
The prior art disclosed in U.S. Pat. Nos. 4,687,471 and 4,772,269 (Twardowski et al '471 and Twardowski et al '269) addressed these problems and solved them partially by use of "swan neck" catheters: 1) exit/tunnel infection by a downwardly directed skin exit, 2) pericatheter leaks by placement of the deep cuff in the rectus muscle, 3) catheter tip migration by caudal direction of the intraperitoneal segment, and 4) outer cuff extrusion by a permanent bend between the cuffs. U.S. Pat. No. 4,935,004 (Cruz '004) utilized similar principles as applied in Twardowski '269 to reduce complications. Results achieved with Cruz '004 are not published yet.
Recently published results obtained with swan neck catheters in four Central Missouri hospitals confirmed theoretical expectations. An overall survival of 64% at 36 months for swan neck catheters was significantly better than that of 29% for "standard" catheters (Twardowski Z.J., Prowant B.F., Khanna R., Nichols W.K., Nolph K.D.: Long term experience with Swan Neck Missouri catheters. ASAIO Transactions 1990; 36: M491-M494.). "Standard" catheters were Tenckhoff (Tenckhoff H., Schechter H.: A bacteriologically safe peritoneal access device. Trans Am Soc Artif Intern Organs 1968; 14: 181-187.14: 181-187) and the Toronto Western Hospital catheter (U.S. Pat. No. 4,392,855).
In spite of this progress the results are still not totally satisfactory, particularly in respect to exit site infections. Although the probability of catheter survival at 3 years (if all complications except of exit/tunnel infections were censored) increased from 0.655 to 0.790, the results indicate that 21 percent of implanted catheters cannot survive 3 years because of exit/tunnel infection (Twardowski Z.J., Prowant B.F., Khanna R., Nichols W.K., Nolph K.D.: Long term experience with Swan Neck Missouri catheters, ASAIO Transactions 1990; 36:M491-M494.). Many exit infections, although not leading to catheter removal, cause patient suffering, require prolonged antibiotic therapy, and increase the cost of treatment.
One of the important reasons for exit site infection is trauma caused by catheter pulling or tugging, pressure on the exit by a tight garment, and the movement of the patient's abdominal wall transmitting mechanical stress to the exit (Twardowski Z.J., Prowant B.F.: Can new catheter design eliminate exit site and tunnel infections? Perspectives in Peritoneal Dialysis. 1986; 4(No. 2): 5-9.). To prevent exit site infection, good catheter protection from mechanical stress is extremely important, especially during break-in; however, all efforts to immobilize the catheter with use of various devices have been only partially successful because the abdominal wall is in constant motion. This motion is transmitted to the catheter, causing a piston like movement within the sinus tract, which traumatizes the skin exit and sinus tract, and brings about bacterial penetration deep into the sinus tract. Damage to the epidermis and/or granulation tissue within the sinus tract combined with the deep bacterial penetration results in infection.
Our extensive clinical and research experience with catheter exit sites indicates that downwardly directed exits of cuffed hemodialysis catheters implanted into jugular and/or subclavian veins are less prone to infection than those of peritoneal catheters (Twardowski Z.J., Prowant B.F., Nolph K.D., Khanna R., Schmidt L.M.: Culture results of peritoneal catheter peri-exit smears (S) and sinus tract washouts (W). XIth International Congress of Nephrology, Abstracts, Tokyo, Japan, July 15-20, 1990, p. 259 A; Twardowski Z.J., Prowant B.F., Nolph K.D.,. Khanna R., Nichols W.K., C.W. Caldwell C.W., H. Taylor H., H.L. Moore H.L.: Key factors in exit site(s) (ES) evaluation. XIth International Congress of Nephrology, Abstracts, Tokyo, Japan, July 15-20, 1990, p. 26 A.). A salient difference between exits of such hemodialysis catheters and those of peritoneal catheters is their location: the chest versus the abdomen. The chest is a very sturdy structure, with minimal wall motions compared with the abdominal wall. The catheter exit located on the chest wall is thus subjected to movement only minimally, therefore is less likely to become infected. Moreover, a tight garment is usually not worn on the chest and there is less pressure on the exit.
There is controversy as to whether the external cuff is beneficial or detrimental for catheter survival. Several authors showed exit site infections to be similar with and without external cuff. Other authors noted that infection became resistant to antibiotic treatment once the tissue grown into the external cuff was infected. They considered the outer cuff to be a detriment rather than an asset for the peritoneal catheter. On the contrary, we found a beneficial effect of the cuter cuff, provided that the cuff was located 1-2 cm from the exit and cuff extrusion was prevented (Twardowski Z.J., Nolph K.D., Khanna R., Prowant B.F., Ryan L.P.: The need for a "Swan Neck" permanently bent, arcuate peritoneal dialysis catheter. Perit Dial Bull 1985; 5: 219-223). Our extensive study of the morphology of the catheter tunnel suggests that the tissue ingrown into the cuff does not constitute per se a critical barrier for spreading infection (Twardowski Z.J., Dobbie J.W., Moore H.L., Nichols W.K., DeSpain J.D., Anderson P.C., Khanna R., Nolph K.D., Loy T.S.: Morphology of peritoneal dialysis catheter tunnels. Accepted for publication to Perit. Dial. Int). This observation suggests that the value of the external cuff depends on anchoring the catheter resulting in the restriction of the piston-like movement. Consequently, another anchoring structure, not a porous cuff, may better prevent exit site infection.
In accordance with this invention, the above disadvantages are reduced by the use of a modified catheter.